#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;

int X, Y, N;
double A[101010];

int main() {
  cin >> X >> Y >> N;
  for (int i = 1; i <= N; i++) cin >> A[i];
  for (int i = 1; i <= N - 1; i++) {
    double T = A[i] / X;
    if (A[i + 1] < T * Y) {
      cout << "NO" << endl;
      return 0;
    }
  }
  cout << "YES" << endl;
  return 0;
}